The present invention relates to a method for checking products with labels.
It is known to provide products with decorations by providing labels thereon. These labels may be adhered to the inside or outside of a product or, preferably, are provided by in-mold labeling technique. These labels moreover, besides providing the decoration, typically afford protection of goods to be packaged in the products, for instance from the influence of light. In this connection it is highly important for the labels to be fitted in the correct manner. In substantially rectangular holder-shaped products, often labels are used that in flat condition have roughly the shape of a Maltese cross, that is, a central surface having four adjoining cross surfaces. The central surface is then placed against the bottom of the holder, the cross surfaces against the four side surfaces of the holder. The cross surfaces must adjoin each other accurately along the ribs of adjacent side surfaces, such that no light can pass between these surfaces and, moreover, any decorations continue across the ribs. If this has been achieved to an insufficient extent, the products are rejected.
Commonly, products are inspected visually. To that end, the products in a production line are looked at by quality inspectors, who remove poorly labeled products from the production line. In more advanced methods, cameras with pattern recognition means are used. The labels are then provided with printings recognizable to the pattern recognition means, which printings can be compared with pre-inputted patterns. In case of insufficient agreement, the product involved is removed. These known methods have the drawback that they are particularly labor-intensive and moreover lead to an undesirably high percentage of errors. In the known method, the use of the pattern recognition means moreover leads to the drawback that only specific patterns are recognizable. Furthermore, for this purpose, a relatively large number of cameras must be used, which is costly and involves susceptibility to trouble.
The invention has for its object to provide a method of the type described in the opening paragraph, in which the above drawbacks of the known methods are avoided, while retaining the advantages thereof. To that end, a method according to the invention is characterized by the measures according to claim 1.
In a method according to the invention, use is made of a light source and light-sensitive means to trace any errors in a product with a label. It has been found that with a method according to the invention errors can be traced particularly fast and accurately. In the method, moreover, use can be made of simple light-sensitive means. Especially if use is made of both measurement of light falling through and of pattern recognition, a particularly high accuracy can be achieved. Moreover, by means of a rejection signal other parts of the same or a different apparatus may be controlled, for instance discharge means for rejected products or means for positioning the labels. Thus, an optimally automated method can be obtained for manufacturing and checking products with labels.
The invention further relates to an apparatus for checking products with labels. According to the invention, such an apparatus is characterized by the features according to claim 7.
In an apparatus according to the invention, use is made of a light source and light-sensitive means to trace any errors in a product with a label. It has been found that with an apparatus according to the invention errors can be traced very fast and accurately and use can be made of simple light-sensitive means. Especially if use is made of both measurement of light falling through and pattern recognition, a particularly high accuracy can be achieved. Moreover, by means of a rejection signal, other parts of the same or a different apparatus may be controlled, for instance discharge means for rejected products or means for positioning the labels.
An apparatus according to the invention is particularly suitable for checking in-mold labeled injection molded products to be used as packages, with both the bottom and the longitudinal walls labeled, and the labels having edge portions adjoining each other, in particular adjacent the ribs of the holder. An apparatus according to the invention is preferably provided with a table having an opening against which or over which the holder can be placed by an open side thereof, the table being provided with an abutment edge around the opening to provide a substantially light-tight seal between the holder and the table. Thus, the desired light-tightness of the holder can be checked particularly fast.
An apparatus according to the invention is preferably provided with a discharge device controlled on the basis of the presence or absence of a rejection signal for a respective product. Thus, products can be automatically conveyed further for later use or be discharged if the labels have not been provided in the correct manner or if other defects are established. The products are preferably supplied by means of belt conveyer means and picked up and displaced within the apparatus with the aid of suction means, at least reduced pressure means, such as suction cups, or the like. By these means, the products can be picked up and displaced simply, rapidly, and accurately, without damage.
An apparatus according to the invention is preferably of such design that at least two products can be handled simultaneously, in particular can be checked simultaneously. Also, the apparatus may be of such design that in each case two juxtaposed feeding and discharge means make use of a checking apparatus disposed between them and comprising the at least one light source and light-sensitive device. Furthermore, it is then preferred that the apparatus be of modular construction, such that it can be easily and rapidly adapted to other types of products.
Further advantageous embodiments of an apparatus and a method according to the invention are described in the subclaims.